#include <bits/stdc++.h>
//#include <ext/pb_ds/detail/standard_policies.hpp>
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
//#pragma GCC optimize("Ofast")
//#pragma GCC target("avx2")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4")
using namespace std;
//using namespace __gnu_pbds;
//template <typename T> using ordered_set = tree <T, null_type, less < T >, rb_tree_tag, tree_order_statistics_node_update>;
mt19937 gen(time(0));
#define ll long long
#define ld long double
#define pb push_back
#define F first
#define S second
#define TIME clock() * 1.0 / CLOCKS_PER_SEC
#define sz(a) int32_t(a.size())
#define endl '\n'
//#define int long long
const int N = 3100;
const int M = 31;
const int mod = 1e9 + 7;
const ll inf = 1e18 + 7;
int a[N][N];
int32_t main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
#ifdef LOCAL
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#else
// freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
#endif // LOCAL
int n, m;
cin >> n >> m;
for(int i = 0; i < n; i++)
for(int j = 0; j < m; j++)
{
char c;
cin >> c;
a[i][j] = int32_t(c - '0');
}
int x = n, y = n, ls = 0;
for(int i = 0; i < n; i++)
{
ls = -1;
for(int j = 0; j < m; j++)
{
if (!a[i][j])
{
if (j && a[i][j - 1]) x = min(x, j - ls - 1);
ls = j;
}
}
if (ls != m - 1) x = min(x, m - ls - 1);
}
for(int j = 0; j < m; j++)
{
ls = -1;
for(int i = 0; i < n; i++)
{
if (!a[i][j])
{
if (i && a[i - 1][j]) y = min(y, i - ls - 1);
ls = i;
}
}
if (ls != n - 1) y = min(y, n - ls - 1);
}
cout << x * y;
}
